Power Supply for 500W+500W Amplifier

wakibaki

Banned
2008-01-08 11:51 pm
Here's a table showing voltage and current @500W for various speakers.

500_amp_psu.jpg

You'll need a transformer with dual output equal to the RMS voltages shown e.g. 45 - 0 - 45 for 4 ohms. The current shown is for one channel only, so 22A+ for 4 Ohms 2 channels. Transformer probably needs to be ~2000VA or greater.

500WPC is a BIG amplifier. I think that if you do not know how to design the power supply you are taking a big risk to build such a big amp.

w
 
The simplest solution is a transformer, bridge rectifier and smoothing capacitors.

do you a schematic or block diagram sir?

You'll need a transformer with dual output equal to the RMS voltages shown e.g. 45 - 0 - 45 for 4 ohms

what kind of transformer? toroidal or just traditional EI Transformer?


heres my problem, i already have a amplifier, and its only 50Wrms, the problem is i bought a wrong speaker set, all of my speaker has a required wattage of allmost 150Wpeak, 2 mid-range 150Wpeak, 1 woofer 200 Wpeak and a tweeter 150Wpeak, so the total is atleast 650watts, is the 500W amplifier overkill or should i reduced it too, 200W?

@Cristi

thanks for the link sir
 

wakibaki

Banned
2008-01-08 11:51 pm
Toroidal or EI, both are acceptable.

Better you should post links showing which speaker drivers you have. Have you built them into an enclosure with a crossover?

150W peak = 75W rms.

You can run these speakers with separate amplifiers, so better to let us know exactly what you've got before going any further.

w
 
Toroidal or EI, both are acceptable.

Better you should post links showing which speaker drivers you have. Have you built them into an enclosure with a crossover?

150W peak = 75W rms.

You can run these speakers with separate amplifiers, so better to let us know exactly what you've got before going any further.

w

i dont have a link for it but this this is there specs,
for woofer KONZERT SG-6W, (150-200W, 60Hz-5KHz, 91 dB SPL, 8 OHMS IMP),
Mid-range KONZERT SG-5M ( 150W, 500Hz-8Khz, 91 dB SPL, Fs=500HZ, and 8 OHMS IMP)
and my Tweeter (5KHz-20KHz, 91 dB SPL, 150W, 8 OHMS IMP)

yes i built it in enlosure with crossover heres the image of my crossover design

2nd Order Reverse Polarity

4000 Hertz / 500 Hertz

8 Ohm Tweeter / 4 Ohm Mid / 8 Ohm Woofer
2.45 db Bandpass Gain, Spread = 8 : 3 octaves

[IMGDEAD]http://www.diyaudioandvideo.com/Calculator/APCXOver/circuit2.gif[/IMGDEAD]
its in 2nd order reverse polarity and here are its parts

Parts List
Capacitors
C1 = 2.46 uF
C2 = 53.85 uF
C3 = 4.38 uF
C4 = 19.7 uF
Inductors
L1 = 0.64 mH
L2 = 2.64 mH
L3 = 0.26 mH
L4 = 5.15 mH

Note: 2 Mid-range speaker are in parallel to my design
 
Hi,
if your three drivers are 100W, 75W & 75W (genuine, long term, no damage, average input power) then an amplifier between 50W and 200W would be about right to drive the speaker.
Certainly not 500W.

I suspect the tweeter is rated to match a 150Wpk speaker system. There are very few tweeters rated to 150Wpk.

To get these range of powers you would need a transformer of 30+30Vac (60W per channel into 8ohms) or 35+35Vac (100W per channel into 8ohms) or 40+40Vac (160W per channel into 8ohms)
 
Last edited:
Just because a driver is rated at a certain power doesn't mean it needs that much power. If you look at the data sheet there is probably a note for the power rating such as "IEC 268-5, via High Pass Butterworth Filter 2500Hz 12 dB/oct." This means that the driver doesn't see the full power of the system driving power. The woofer rating is usually it's thermal rating. Depending on the enclosure, you may reach xmax before you reach the thermal limit.

If this is for PA use, limit your amp to 200W. Don't go too much lower or you may drive it into clipping and fry the tweeter. For home use you can get away with a lot less power. 45v-0-45V @ 1KVA is about where you should be for PA use. For home use, follow one of Andrew T's suggestions, at 4-500VA.

You may also want to start a thread in the mutli-way speaker forum to get some help with your XO. At a minimum you'll want to pad down the mids, since a pair in parallel gets you 97 db/2.83V sensitivity. Unless the cabinet is very wide or placed very close to the wall, you'll probably want to add some baffle step compensation. Have you measured the response of your drivers in the cabinet?
 
thank you BobEllis and AndrewT that enlightened me up,:cheers:

i guess ill have to stepdown my amplifier to 200Watts, i found here a 200W amplifier that requires 50v+50v supply, is this good?

My design is for my personal use (Home Theater, etc....), i already made my enclosure and test the whole system in the audio shop where i bought the speakers, it sounds good and i feels like im watching on cinema. . . .

since a pair in parallel gets you 97 db/2.83V sensitivity

really? do i need to put a loss pad to reduce its sensitivity?

Have you measured the response of your drivers in the cabinet

how sir? i dont know too measure it, i have little knowledge about speaker system.:sad:

i guess i have to make a new thread for my XO,

so i think this is my last question,
is 50v-50v 500VA good?
how many capacitors do i need?
how much capacitance i need? and how about audio hum?
how can i remove or prevent it?:confused::confused::confused:
 
I found here a 200W amplifier that requires 50v+50v supply, is this good?
Hi,
this is not good.

They have missed some information from the specification to make it useful.
This indicates the seller is hiding behind the numbers and trying to catch out the unwary.

A +-50Vdc power supply should allow ~100W into 8ohms.
One can only get 200W into 4ohms, but few retail/commercial amplifiers can actually achieve. Too many compromises in component selection to get the price down.

If you settle for a 40+40Vac transformer you should get between 150W and 170W into 8ohms. This can use 63Vdc capacitors and that saves money.

If you decide to set your target at 200W then you must use a a higher voltage transformer (45+45Vac will meet the power target) and this will require 75Vdc or 80Vdc capacitors.
is 50v-50v 500VA good?
I think you are confusing AC and DC voltages.

The mains and the transformer output are AC voltages, eg. 230:30-0-30Vac.
This will give a DC power supply for an amplifier of about +-42Vdc, good for 60 to 80W into 8ohms.

A 50-0-50Vac transformer will give about +-70Vdc, good for 250 to 280W into 8ohms.
how about audio hum?
how can i remove or prevent it
read the article linked on the home page of the Forum.
 
Last edited:
I'll second the 40VAC recommendation, lower voltage makes it a little safer to deal with as a first project. Not to mention 150W is only 1.2 dB less headroom than 200W.

A rule of thumb is 1,000 uf per rail for each 10 W of output for a class AB amp. 10,000 to 20,000 uf per rail in each channel should be ok.
 
I think you are confusing AC and DC voltages.

The mains and the transformer output are AC voltages, eg. 230:30-0-30Vac.
This will give a DC power supply for an amplifier of about +-42Vdc, good for 60 to 80W into 8ohms.

A 50-0-50Vac transformer will give about +-70Vdc, good for 250 to 280W into 8ohms.

im sorry sir typo error i should put 50-0-50, not 50-50, sorry about that:headbash:.
:( (sigh) i need to find an 200w amplifier that require a 40+40,

thank you guys for your replies, once i bought 200w amplifier i will start designing my powersupply.

thanks to BobEllis and AndrewT your replies help a lot.:cheers:
 
can you use a calculator?

enter 56.6.
multiply by 7.07.
answer = 400.16
That is the peak power at the instant that peak voltage is 56.6 and peak current is 7.07 into an 8r0 load.
The average power is half of this peak power value.
Divide by 2.
Answer = 200.08

This is using the formula Power = Volts * Amps

There are other formulae that give exactly the same answer.
P = I^2 * R
P = V^2 / R

If you want to work with root mean squared (rms) values then divide the peak values by sqrt(2). This formula (Vpk = Vrms * sqrt(2) ) applies to all sinewave signals.

56.6Vpk = 40Vac
7.07Apk = 5Aac

P = V*A = V^2/R = I^2*R
 
Pitt,

Why the 200W hangup? You probably don't need 200W in any home application other than subwoofer duty.

Are you planning to by an amp module/kit that claims 200W out? or are you looking to build something from scratch? If scratch built look for a project with boards available that will give you 100W or so. I like the Leach amp - there may be some updated boards available.